1. Technical Field
The present disclosure relates to a manufacturing method of an optical waveguide.
2. Related Art
With the increase in the speed (frequency) of the signal transmission, various electronic circuits have come to employ optical/electrical hybrid circuits where conductive interconnections of copper or the like are replaced with optical interconnections using optical waveguides in part of the circuit.
In optical/electrical hybrid circuits of this type, a light-emitting element such as a vertical cavity surface emitting laser (VCSEL) and a light-receiving element such as a photodiode (PD) are mounted on a circuit board and light that is emitted from the light-emitting element is transmitted to the light-receiving element via an optical waveguide.
In optical/electrical hybrid circuits, light that is emitted from the light-emitting element perpendicularly toward the circuit board is reflected by a mirror portion that forms an angle 45° with respect to the light traveling direction so as to travel in parallel with the circuit board (the traveling direction is changed by 90°) and thereby travels through the optical waveguide.
For example, JP-A-2006-139119 describes a method for manufacturing an optical waveguide having the above-mentioned mirror portion using a die. In this manufacturing method, the mirror portion and a core layer for propagating light are formed by using a die. More specifically, the mirror portion and the core layer are formed by filling grooves of the die with liquid ultraviolet-setting resin and then irradiating the resin with ultraviolet light.
However, in the manufacturing method disclosed in JP-A-2006-139119, when the grooves of the die are filled with liquid ultraviolet-setting resin, the resin overflows the grooves and is set in the overflowed state. It is therefore necessary to remove the overflowed parts of the resin. Furthermore, the manufacturing process as a whole of an optical waveguide is complex because the core layer and cladding layers that surround the core layer are produced by different manufacturing methods, that is, whereas the core layer is formed by using the die, the cladding layers are formed by laminating resin sheets. Still further, the die is formed with the grooves having complex shapes for forming the mirror portion and the core layer, respectively, and hence it is difficult to produce such a die with high dimensional accuracy. Moreover, there is possibility that liquid ultraviolet-setting resin does not reach every corner of the grooves having certain shapes and dimensions.